1. Field of the Invention
The present invention relates to a molding machine for manufacturing shaped articles comprised of a polymeric material, such as composite electrical insulators. More particularly, the present invention pertains to an apparatus for reliably removing a shaped article from the mold halves, which is compact and simple in structure.
2. Description of Related Art
There is known a composite electrical insulator which can be obtained by integrally providing an elongate core rod of fiber-reinforced plastics (FRP) with a sheath and sheds by injection or transfer molding of appropriate polymeric material having an electrically insulating property, such as silicone rubber, ethylene propylene copolymer (EPM), ethylene propylene diene copolymer (EDPM), polyurethane, etc. Such a composite insulator has been actually put into practical applications, particularly in any use environment which can draw out various functional advantages of the composite insulator.
In order to manufacture composite insulators, there is typically used a mold assembly which includes upper and lower mold halves defining a mold cavity when they are tightened and thereby closed. The polymeric material for the composite insulator tends to remain attached to the mold halves, even when a releasing agent is applied to the inner surface of the mold cavity before the molding step. Thus, when the molding halves are being opened, the composite insulator as a whole or in its end portion may remain attached to the upper mold half. When the entire composite insulator remains attached to the upper mold half, the composite insulator has to be removed from the upper mold half by performing a troublesome manual operation on the parting surface on the lower side of the upper mold half, while carefully preventing the composite insulator from being dropped onto the lower mold half. On the other hand, when the end portion of the composite insulator remains attached to the upper mold half, the composite insulator may be applied with a severe twisting force or it may be dropped onto the lower mold half during the opening process of the mold, so that the core rod and/or sheds of the composite insulator may be subjected to deformation or damages.
In order to avoid these drawbacks, it has been a typical practice to insert an appropriate tool into a space between the upper and lower mold halves as they are slightly opened, so as to urge the composite insulator against the lower mold half while displacing the upper mold half away from the lower mold half, and thereby remove the composite insulator from the upper mold half. On this instance, when the composite insulator is in tight attachment to the upper mold half, it may still be applied with a severe twisting force during removal of the composite insulator.
An alternative approach is to temporarily connect retainer rings to the end portions of the core rod, which are then detachably connected to the lower mold half so that the composite insulator can be forcibly removed from the upper mold half as the latter is displaced away from the lower mold half. However, this approach requires additional manual steps to be performed during preparation of molding and upon removal of the composite insulator.